Alternate fuels have been developed to mitigate the rising prices of conventional fuels and for reducing exhaust emissions. For example, natural gas has been recognized as an attractive alternative fuel. For automotive applications, natural gas may be compressed and stored as a gas in cylinders at high pressure. A pressure regulator may then be used to supply the compressed natural gas (CNG) at lower pressures to an engine combustion chamber via a fuel injector. During engine start-up, the fuel rail supplying fuel to the fuel injector may experience an over-pressure event. This over-pressurized fuel rail may create a large pressure differential across the inward-opening injector, inhibiting opening of the injector and delaying (or preventing) engine start. Further, during engine cranking, less voltage (and thus the current that provides injector opening force) may be available at the injector than during engine running conditions. Thus, extra current which may provide extra force to overcome the pressure differential and open the injector is not available.
The inventors herein have recognized that reducing the pressure differential across the injector opening reduces the amount of current needed to open the injector, thus enabling more reliable injector opening during engine start-up. Accordingly, a method for starting an engine is provided. The method comprises opening a throttle valve controlling air flow into an intake manifold in response to a gaseous pressure differential across a gaseous fuel injector exceeding a threshold pressure.
In this way, the throttle valve may be opened responsive to a high pressure differential across the gaseous fuel injector. By opening the throttle valve, the intake manifold pressure may increase, reducing the pressure differential across the injector. The reduced pressure differential in turn reduces the amount of current that is required to open the fuel injector. Thus, during an engine start or other condition where a gaseous fuel injector is activated during high fuel rail pressure, the injector may be rapidly opened, mitigating delayed engine starts.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.